Comment 3 for bug 1827690

Doing some research.

1) I don't think this is more than one charm unit trying to do migrations at the same time (comment #2)
2) The problem is barbican itself failing per the Traceback
3) My current theory is a failed migration attempt that leaves behind two alembic versions.

Per [1] we should only ever expect 1 alembic version at a time. As a work around we may need to do some DB surgery per [1]. After a backup of course.

To find what gets barbican into this state will take a bit more digging through logs.

[1] https://stackoverflow.com/questions/42424320/how-do-i-fix-alembics-requested-revision-overlaps-with-other-requested-revisio